The primary function of the lungs is breathing and gas exchange. Air is primarily taken into the lungs during inhalation by contraction of the diaphragm, and also by upward and outward movement of the ribs, and outward movement of the sternum. The size of the chest cavity increases, allowing the lungs to expand. When inhalation is complete, the central nervous system signals the respiratory center in the brain that enough air has entered the lungs and exhalation occurs. During exhalation, the diaphragm relaxes and the ribs move down and in, lessening the size of the chest cavity. As the lungs are “squeezed,” volume is reduced. The diaphragm returns to its original position. Negative pressure is always present within the pleural or chest space and creates a vacuum or suction called intrapleural pressure. This vacuum keeps the lungs against the chest wall, preventing lung collapse even during forced exhalation. Intrapleural pressure is always slightly negative compared to atmospheric pressure. When this intrapleural pressure is lost or disrupted, the lung collapses.
Lung tissue is a very delicate organ and structure. Any penetration of the pleura or the lung parenchyma typically results in air leakage (pneumothorax) and bleeding (hemothorax). When the lung is damaged and leaks air, the lung collapses because of the loss of vacuum in the chest cavity, and because accumulation of air in the thorax cavity mechanically compresses the lung. If there is only a minimal amount of air accumulated, it can be reabsorbed. This is commonly the case with small blunt trauma, in which the lung ruptures and then heals itself quickly. When more than a minimal amount of air has accumulated, or when a persistent or continuous leakage of air either out of the lungs or into the chest cavity from an external opening exists, the pneumothorax is generally resolved by the placement of chest tubes connected to a vacuum drain system or a valve. When a severe penetrating thoracic trauma occurs and severe pneumothorax and hemothorax are observed, surgical tissue repair may be indicated. Unresolved and untreated large pneumothorax could be fatal
Disruption of the sealed pleural and thoracic space always occurs during thoracic surgery. Prolonged and extensive air leaks are frequently observed after thoracic surgery that involves resection of diseased lung tissue. In addition, disruption can also be produced by trauma, lung surgery or surgery of adjacent organs with inadvertent lung tissue perforation. Occasionally, spontaneous pneumothorax is observed in patients with severely diseased tissue after chest trauma or a cough. Even without disruption of the pleural and thoracic space, post-operative care after surgery involving the heart or other organs near the plural cavity usually includes placement of chest tubes and application of a vacuum drain to evacuate air and re-establish the negative pressure to ensure lung expansion.
For many years, the standard apparatus for draining the pleural or chest cavity was a vacuum drainage system known as the “3-bottle set-up” which includes a collection bottle, a water-seal bottle, and a suction-control bottle. The three bottles are connected in series by various tubes to apply suction to the pleural cavity to withdraw liquid and air, and discharge the fluid into the collection bottle. A chest tube runs from the patient's pleural cavity to the collection bottle, and the suction bottle is connected by a tube to a suction source. Air withdrawn from the chest cavity first enters the collection bottle, and then passes into the water-seal bottle, where it bubbles through water in the water-seal bottle. The water in the water seal also acts as a one-way valve preventing back flow of air into the chest cavity, and as an escapement mechanism for evacuation air flow. The suction level is regulated by filling the suction-control bottle with water to a desired level. Suction pressure or vacuum is usually provided by a central vacuum supply in a hospital to permit withdrawal of fluids such as blood, water and air from a patient's pleural cavity. The suction establishes a pressure differential between the suction source and the internal pressure in the patient's chest. This system is sometimes known as an “underwater” or “wet” system because water is used in the suction-control chamber.
Various inefficiencies existed in the 3-bottle set-up resulting from the many separate components, the large number of connections, and complications in its use. About 30 years ago, the 3-bottle set-up lost favor with the introduction of an underwater-seal drainage system that employed a single, pre-formed, self-contained unit that embodies the 3-bottle techniques with three separate chambers performing the same functions. The desired suction level is established by the water level in the suction-control chamber. The single, preformed unit is easily portable and is disposable.
“Dry” or “waterless” chest drain systems were developed to address the perceived shortcomings of the “wet” or “underwater” systems. The dry systems follow the same fundamental principles of the wet systems including the water-seal chamber, but use a plurality of valves to control suction pressure instead of a wet suction chamber.
An important aspect of treating a patient with a pneumothorax is to know the status of any air leak. This includes the rate of air being leaked into the chest cavity and when it leaked. It is also important to know whether air is entering into the chest drain system from a source other than the patient, such as a system leak. This information is obtained by observing bubbles in the water-seal chamber presently used by both the current underwater and waterless chest drain systems. As the vacuum draws air and liquid from the chest cavity, air from the chest cavity flows through the water seal and creates bubbles. To determine the rate at which air is being evacuated from the patient, an observer must observe and estimate the number of bubbles created in the water seal. If the observer sees continuous bubbling, a persistent air leak exists. If the observer sees intermittent bubbling, an intermittent leak exists, and no bubbling indicates no air leak exists. Graduated air leak monitors have been incorporated into chest drain systems to assist the observer in monitoring and quantifying patient air leak trends. However, no present apparatus or method exists for determining the rate at which air is being evacuated from a patient without a person actually observing the water-seal portion of the chest drain system. Furthermore, no present apparatus exists for providing a history of the patient's air evacuation, sounding an alarm if the air evacuation rises above a predetermined level, or if the chest drain becomes occluded or fails.
Furthermore, patients frequently have intermittent air leaks that may be missed or misinterpreted if the observer was not present when they occurred. Because of unrecognized intermittent air leaks, many patients require re-placement of chest tubes after the tubes were removed, creating increased morbidity and cost. Therefore, the present system of chest tube monitoring does not adequately provide a continuous monitoring system. Another unrecognized complication is the chest tube becoming plugged or accidentally kinked, impairing its function and causing an observer to assume that the air leak has stopped because no bubbles are observed.
In view of the foregoing, there is a need in the art for a new and improved apparatus and method for improving the monitoring of evacuation of air by a chest drain without the need for constant visual observation of the bubbles. There is also a need for providing trending information, and for providing an alarm when excessive air leaks occur or when air evacuation suddenly stops. The present invention is directed to a device, system, and method that provide such an improved apparatus and method for monitoring chest air evacuation.